Currently, a digital terminal (such as an integrated access device (IAD)) can not only provide an Internet access service for a user, but also provide a voice service for the user. However, in a process in which the digital terminal provides the voice service for the user, when a fault occurs in an upper-layer network of the digital terminal, registration of the voice service of the digital terminal fails. After the registration of the voice service of the digital terminal fails, the digital terminal performs a first registration retry according to a Session Initiation Protocol (SIP) standard to detect whether the upper-layer network of the digital terminal has been recovered from the fault. If the digital terminal determines that the first registration retry fails, the digital terminal waits for T seconds and performs a second registration retry. If the digital terminal determines that the second registration retry fails, the digital terminal waits for 2T seconds and performs a third registration retry, and so on. If the digital terminal determines that the nth registration retry fails, the digital terminal waits for n*T seconds and performs an (n+1)th registration retry, until a maximum time interval is reached. Subsequently, registration retries are performed according to the maximum time interval until the registration succeeds, and after the registration of the voice service of the digital terminal succeeds, the user can normally use the voice service.
However, in a period when the digital terminal waits to perform a next registration retry, if the upper-layer network of the digital terminal is recovered from the fault, because a detection time is not reached yet, the digital terminal does not initiate a voice service registration request, and consequently, the voice service cannot be recovered in time.